The present invention relates to a nozzle for a fluidized bed firing system, in which a hood surrounds that end of a coal/air mixture transport pipe which extends into the fluidized bed. An axial exit cross-section is present between the hood and the pipe.
Such a nozzle allows the mass stream to be directed towards the bottom of the fluidized bed. During an interruption of operation, the whirled-up bed material is, moreover, prevented from trickling backwardly into the pipe. The pipes of prior art nozzles of this kind (DE-OS 23 35 514; German application laid open to public inspection before an examination) are provided with lateral openings. This design presents some disadvantages. To quote examples: the dust contained in the mixture causes wear to the hood wall which is situated oppositely to the lateral openings of the pipe. As the cross-section of the openings is smaller than the pipe cross-section, throttling occurs during the exit from the openings.
The present invention pursues the object of altering the flow conditions so as to avoid the disadvantages inherent in a nozzle of the aforementioned kind.
Another object of the present invention is to provide an arrangement of the foregoing character which is substantially simple in construction and may be economically fabricated.
A further object of the present invention to to provide an arrangement, as described, which may be readily maintained in service and which has a substantially long operating life.